'\" t
.TH "SD_EVENT_SOURCE_SET_USERDATA" "3" "" "systemd 256.7" "sd_event_source_set_userdata"
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.SH "NAME"
sd_event_source_set_userdata, sd_event_source_get_userdata \- Set or retrieve user data pointer of event sources
.SH "SYNOPSIS"
.sp
.ft B
.nf
#include <systemd/sd\-event\&.h>
.fi
.ft
.HP \w'void*\ sd_event_source_set_userdata('u
.BI "void* sd_event_source_set_userdata(sd_event_source\ *" "source" ", void\ *" "userdata" ");"
.HP \w'void*\ sd_event_source_get_userdata('u
.BI "void* sd_event_source_get_userdata(sd_event_source\ *" "source" ");"
.SH "DESCRIPTION"
.PP
\fBsd_event_source_set_userdata()\fR
may be used to set an arbitrary user data pointer for the event source object specified as
\fIsource\fR\&. The user data pointer is usually specified when creating an event source object with calls such as
\fBsd_event_add_io\fR(3)
or
\fBsd_event_add_time\fR(3), and may be updated with this call\&. The user data pointer is also passed to all handler callback functions associated with the event source\&. The
\fIuserdata\fR
parameter specifies the new user data pointer to set, the function returns the previous user data pointer\&. Note that
\fBNULL\fR
is a valid user data pointer\&.
.PP
\fBsd_event_source_get_userdata()\fR
may be used to query the current user data pointer assigned to the event source object
\fIsource\fR\&.
.SH "RETURN VALUE"
.PP
On success,
\fBsd_event_source_set_userdata()\fR
and
\fBsd_event_source_get_userdata()\fR
return the previously set user data pointer\&. On failure, they return
\fBNULL\fR\&.
.SH "NOTES"
.PP
Functions described here are available as a shared library, which can be compiled against and linked to with the
\fBlibsystemd\fR\ \&\fBpkg-config\fR(1)
file\&.
.PP
The code described here uses
\fBgetenv\fR(3), which is declared to be not multi\-thread\-safe\&. This means that the code calling the functions described here must not call
\fBsetenv\fR(3)
from a parallel thread\&. It is recommended to only do calls to
\fBsetenv()\fR
from an early phase of the program when no other threads have been started\&.
.SH "HISTORY"
.PP
\fBsd_event_source_set_userdata()\fR
and
\fBsd_event_source_get_userdata()\fR
were added in version 229\&.
.SH "SEE ALSO"
.PP
\fBsd-event\fR(3), \fBsd_event_add_io\fR(3), \fBsd_event_add_time\fR(3), \fBsd_event_add_signal\fR(3), \fBsd_event_add_child\fR(3), \fBsd_event_add_inotify\fR(3), \fBsd_event_add_defer\fR(3), \fBsd_event_source_set_description\fR(3)
